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## Background

Basal Metabolic Rate (BMR)
Basal metabolic rate (BMR) is the amount of energy required to maintain the body's normal metabolic activity, such as respiration, maintenance of body temperature (thermogenesis), and digestion. Specifically, it is the amount of energy required at rest with no additional activity. The energy consumed is sufficient only for the functioning of the vital organs such as the heart, lungs, nervous system, kidneys, liver, intestine, sex organs, muscles, and skin.

Variance:
The resting and basal metabolic rate generally decrease with age or if there is a decline in lean body mass. Activities that tend to increase muscle mass (lean tissue) such as body building or strength training (anaerobic activities), will also increase the basal or resting metabolic rate. Aerobic activities such as running, skating, or rope jumping may improve endurance but have little effect on the basal or resting metabolic rate (see post-exercise expenditure below). Other factors that may affect the BMR or RMR include stress, illness, hormone levels (e.g. thyroid), environmental (e.g. temperature or altitude) or any other factor that effects the normal functioning of one or more vital organs.

Lean tissue requires significantly more energy to maintain because of the increased level of metabolic activity. In contrast, fat tissue requires very little energy to maintain and has little influence on the resting or basal metabolic energy needs.

Greater lean body mass = Greater BMR or RMR.

Because individuals can increase their total lean body mass through strength training (corresponding increase in skeletal muscle), it is possible to increase the overall basal energy requirements at rest.

Age     Gender:

Weight

## Activity Level:

Select preference:

Current daily activity level?

or
Select a custom stress/activity factor:

Definition of activity levels:  The  activity level above will be used along with the BMR derived from the Schofield equation to calculate an estimate of the daily energy needs (kcal/day)

## Activity / Stress factors:

#### Activity Levels:

Male stress factor Female stress factor
Sedentary.  Little to no exercise.  Inactive in both work and leisure. 1.3 1.3
Lightly active: Intensive exercise for at least 20 minutes once or twice per week or daily routine includes some walking.  Example: student.  Generally you do not exercise regularly, but you maintain a busy life style that requires you to walk frequently for long periods. 1.6 1.5
Moderately active: Intensive exercise for at least 20 to 45 minutes 3 to 4 times per week or a job with a lot of walking, or a moderate intensity job. 1.7 1.6
Very active: Intensive exercise for 60 minutes or greater 5 to 7 days per week.  Labor-intensive occupations also qualify for this level.  Labor-intensive occupations include construction work (brick laying, carpentry, general labor, etc.). Also farming, landscape worker or similar occupations. 2.1 1.9
Extremely active: Exceedingly active and/or very demanding activities:  Examples include:  athlete with an almost unstoppable training schedule with multiple training sessions throughout the day or a very demanding job, such as shoveling coal or working long hours on an assembly line. Generally, this level of activity is very difficult to achieve. 2.4 2.2

## Dieting - BMR - RMR Calculators:

Several of these calculators may be particularly useful for dieters.  Just about every single MAJOR calorie/ energy equation that has been released over the last 90 years is included below.   Each calculator has a customized printout option for easy analysis.  Recommendation: Try each calculator - print out the results -  then compare!

Estimated 'Calorie' Calculators:

Harris-Benedict Equation:  Estimation of total calories needed. MOST widely used equation for calculating basal metabolic rate and total calories.
Revised Harris-Benedict Equation:The original Harris Benedict equation was revised in 1984.  This updated equation can be used to calculate the basal metabolic rate and total calories.
RESTING Metabolic Rate (RMR): Resting Metabolic Rate Calc - This equation can be used to calculate the RESTING metabolic rate and total calories. Mifflin-St Jeor equation.
Schofield equation (BMR) : This equation was part of the previous government guidelines to formulate RDA's and can be used to calculate the basal metabolic rate and total calories needed.
Institute of Medicine Equation- LATEST EQUATION: IOM Equation-Estimated Energy Requirement (EER) Estimation of total calories needed. This equation is behind the 2005 Dietary Guidelines for Americans and the new food pyramid, MyPyramid.

Check out the new BMR multi-calc.

## Equations

The Schofield Equation allows one to  estimate the basal metabolic rate (BMR) in calories based on a few simple variables:  gender, age, and weight.  Height is not required.  The final result is given as a range and is adjusted upward or downward from the calculated value based on the 'standard error of estimated' or SEE (provided by the author).  Individuals that have a much higher lean body mass (reduced body fat), should use the upper end of the range, while individuals with a greater body fat percentage should use the lower end of the range.

These equations were also published in 1989 in the government dietary guidelines and were used to formulate the recommend daily allowances (RDA's) for energy needs.  In 2002, these equations were replaced by the Institute of Medicine (IOM) equations.

#### Schofield - Basal Metabolic Rate equations:

 Age (years) Males Females 10-17 BMR = 17.686 x (wt kg) + 658.2 SEE = 105 BMR = 13.384 x (wt kg)  + 692.6 SEE = 111 18-29 BMR = 15.057 x (wt kg) + 692.2 SEE = 153 BMR = 14.818 x (wt kg)  + 486.6 SEE = 119 30-59 BMR = 11.472 x (wt kg) + 873.1 SEE = 167 BMR = 8.126 x (wt kg)  + 845.6 SEE = 111 ≥ 60 BMR =11.711 x (wt kg)  + 587.7 SEE = 164 BMR =9.082 x (wt kg)  + 658.5 SEE: 108 SEE = Standard error of estimation

## BMR

Basal metabolic rate (BMR) is the amount of energy required to maintain the body's normal metabolic activity, such as respiration, maintenance of body temperature (thermogenesis), and digestion. Specifically, it is the amount of energy required at rest with no additional activity. The energy consumed is sufficient only for the functioning of the vital organs such as the heart, lungs, nervous system, kidneys, liver, intestine, sex organs, muscles, and skin.
 Brain: 19% Heart: 7% Kidneys: 10% Liver: 27% Skeletal muscle: 18% Other: 19%

Post-exercise energy expenditure: the amount of additional energy (above the resting or basal metabolic needs) expended after an activity depends on the intensity and duration of the exercise session. More intense sessions tend to increase resting energy needs for longer time periods. These increased energy requirements occur during the cool-down phase and are short-lived. Sustained increases in the resting or basal metabolic rate can only be obtained through regular strength training routines that increase lean body mass.

Summary:
Aerobic activity: short lived increases in RMR/BMR (cool-down period)
Anaerobic activity (regular): increases in lean body weight (LBW) --> Sustained increases in RMR/BMR.

## Utilization

Utilization
: The baseline BMR or RMR can be used along with stress/activity factors to estimate the daily caloric needs of an individual - (Total Energy Expenditure (TEE)  (kcal/day)).   See error rate below.

Total Energy Expenditure (TEE)
The total energy expenditure (amount of calories needed per day) is composed of three primary factors: (1) Resting or basal metabolic rate   (2) Thermic effect of food  (3) Activities of daily living (ADL) - physical activity.

Thermic effect of food (TEF):
Rough estimation: TEF = Total calories consumed/day x 0.1
Example: 2000 kcal diet.    TEF = 2000 x 0.1 = 200 kcal/day.

TEF of protein >>carbohydrates>>fats.

Graphical representation:

## Measurement versus predictive equations:

Direct measurement:  Method: direct or indirect calorimetry.
BMR:   Conditions: measured under very restrictive circumstances  and strict adherence to  protocols. This method is generally impractical in most cases.
RMR:  less restrictive conditions and more easily obtained.  The resting metabolic rate is only marginally different from the BMR.

Predictive equations:
An alternative method is to use predictive equations that can provide a rough estimate of the basal or resting metabolic rate.  The basal or the resting metabolism is the largest component of the total energy expenditure (TEE).... usually 60 - 75%.  The RMR or BMR is usually at the higher end of this range for sedentary individuals (70-75%) and at lower the end for athletes.

## Error rate of predictive equations:

The various predictive equations for determining the resting or basal metabolic rates may significantly under or overestimate the total calories needed to maintain the current weight of an individual when combined with stress/activity factors that are selected by the user. This variance can approach 20% (over or underestimation) depending on differences in  body composition (lean versus obese),  actual activity levels (athletic versus sedentary lifestyle), and energy levels expended in thermogenesis.

## Reference

Schofield WN. Predicting basal metabolic rate, new standards and review of previous work. Hum Nutr Clin Nutr. 1985;39 Suppl 1:5-41. https://www.ncbi.nlm.nih.gov/pubmed/4044297

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